This invention relates to the control of sediment. The term “sediment” is used herein to denote solid particulate material, e.g. soil, sand or pebbles, which can become suspended, or which is suspended, in a flowing stream of liquid, and which will settle out of the liquid when the liquid ceases to flow. The term “sediment control device” (often abbreviated herein to SCD) is used herein to denote an article which can be transported and placed (i) on top of a substrate, usually the ground, in order to collect sediment from a sediment-bearing stream of liquid, usually water, which passes through the SCD, or (ii) around an existing land mass composed of, for example, soil, sand, pebbles or rocks, in order to prevent or reduce removal of sediment from the land mass by water flowing towards, along, over or through the land mass. The term “land mass” is used herein to include, but is not limited to, a slope, a gully, a beach, or the bank of a body of water, e.g. a river or lake.
It is often desirable to collect sediment from liquid in which it is suspended, or to stabilize an existing mass of sediment to prevent it from being carried away. In some cases, the law requires removal of sediment from liquid flowing out of a construction site. The conventional method for collecting sediment is to place hay bales or fiber rolls across the path of the liquid. Other methods are described in, for example, the related patent and applications incorporated by reference above (which were published after the priority date of this application) and U.S. Pat. Nos. 6,422,787, 6,547,493 and 6,641,335, the disclosures of which are also incorporated herein by reference.
The earlier related patent and applications referred to in the Cross-Reference section above describe sediment control rolls (SCRs) comprising                1) an elongate threshold member having a multiplicity of relatively large threshold apertures therethrough;        2) an elongate outflow member having a multiplicity of relatively large outflow apertures therethrough;        3) an elongate filter which has a multiplicity of relatively small filter apertures therethrough, and which preferably is supported by the outflow member, and        4) a location member;the threshold member, outflow member, filter, and location member being secured together so that, when the location member is placed on a horizontal substrate,        (a) an upright member comprising the threshold member, the filter and the outflow member extends upwards from the substrate, and        (b) liquid flowing over the location member towards the upright member passes through the threshold member, the filter and the outflow member.The term “sediment control device (or SCD) which comprises (or comprising) said combination” is used in this specification to denote an SCD comprising, in combination, a threshold member, an outflow member, a filter and a location member as described above. The SCRs described in the earlier related patent and applications contain a substantially hollow elongate sediment control chamber (SCC) which lies between the threshold member and the outflow member, the term “substantially hollow” being defined to mean that the SCC has an unobstructed volume which is at least 50%, e.g. 50 to 98%, of the total volume of the SCR. The term SCD is used in this specification, in preference to the term SCR, because the SCDs of the present invention, although they often contain a substantially hollow SCC as defined in the earlier related patent and applications, do not necessarily contain a substantially hollow SCC.        
As noted in the earlier related patent and patent applications referred to above, SCDs are preferably both strong and flexible, so that they will not be rendered ineffective by rough treatment of the kind that is difficult to avoid at construction sites, for example people standing on, and vehicles passing over, the SCD.